Thin dual-aperture zoom digital camera

ABSTRACT

A dual-aperture zoom camera comprising a Wide camera with a respective Wide lens and a Tele camera with a respective Tele lens, the Wide and Tele cameras mounted directly on a single printed circuit board, wherein the Wide and Tele lenses have respective effective focal lengths EFL W  and EFL T  and respective total track lengths TTL W  and TTL T  and wherein TTL W /EFL W &gt;1.1 and TTL T /EFL T &lt;1.0. Optionally, the dual-aperture zoom camera may further comprise an optical OIS controller configured to provide a compensation lens movement according to a user-defined zoom factor (ZF) and a camera tilt (CT) through LMV=CT*EFL ZF , where EFL ZF  is a zoom-factor dependent effective focal length.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of U.S. patentapplication Ser. No. 14/973,753 filed Dec. 18, 2015 (now allowed) whichwas a Continuation application of U.S. patent application Ser. No.14/373,500 filed Jul. 21, 2014 (issued as U.S. Pat. No. 9,413,972) whichwas a U.S. National Stage application under 35 USC 371 frominternational patent application PCT/IB2014/062854 filed Jul. 4, 2014,and is related to and claims priority from U.S. Provisional PatentApplication No. 61/842,987 titled “Miniature telephoto lens assembly”and filed Jul. 4, 2013, which is incorporated herein by reference in itsentirety.

FIELD

Embodiments disclosed herein relate in general to digital cameras, andmore particularly, to thin dual-aperture zoom digital cameras that canbe incorporated in a portable electronic product such as a mobile phone.

BACKGROUND

Compact multi-aperture and in particular dual-aperture (also referred toas “dual-lens” or “dual-camera”) digital cameras are known.Miniaturization technologies allow incorporation of such cameras incompact portable electronic devices such as tablets and mobile phones(the latter referred to hereinafter generically as “smartphones”), wherethey provide advanced imaging capabilities such as zoom, see e.g.co-owned PCT patent application No. PCT/IB2013/060356 titled“High-resolution thin multi-aperture imaging systems”, which isincorporated herein by reference in its entirety. A two-camera system(exemplarily including a wide-angle (or “Wide”) camera and a telephoto(or “Tele”) camera) is calibrated in an end product (e.g. in asmartphone) after manufacturing.

System calibration matches Tele and Wide image pixels by capturing inboth cameras known objects. This enables faster and more reliableapplication of fusion between the two cameras, as described inPCT/IB2013/060356. One problem with such cameras may arise from mishapssuch as drop impact. The latter may cause a relative movement betweenthe two cameras after system calibration, changing the pixel matchingbetween Tele and Wide images and thus preventing fast reliable fusion ofthe Tele and Wide images.

Another problem with dual-aperture zoom cameras relates to their height.There is a large difference in the height (also known as total tracklength or “TTL”) of the Tele and Wide cameras. The TTL, see FIG. 1, isdefined as the maximal distance between the object-side surface of afirst lens element and a camera image sensor plane. In the following,“W” and “T” subscripts refer respectively to Wide and Tele cameras. Inmost miniature lenses, the TTL is larger than the lens effective focallength (EFL), which has a meaning well known in the art, see FIG. 1. Atypical TTL/EFL ratio for a given lens (or lens assembly) is around 1.3.In a single-aperture smartphone camera, EFL is typically 3.5 mm, leadingto a field of view of 70-80°.

Assuming one wishes to achieve a dual-aperture X2 optical zoom in asmartphone, it would be natural to use EFL_(W)=3.5 mm andEFL_(T)=2×EFL_(W)=7 mm. However, without spatial restrictions, the Widelens will have an EFL_(W)=3.5 mm and a TTL_(W) of 3.5×1.3=4.55 mm, whilethe Tele lens will have EFL_(T)=7 mm and TTL_(T)of 7×1.3=9.1 mm. Theincorporation of a 9.1 mm lens in a smartphone camera would lead to acamera height of around 9.8 mm, which is unacceptable for manysmartphone makers. Also the large height difference (approx. 4.55mm)between the Wide and Tele cameras can cause shadowing and light-blockingproblems, see FIG. 2.

A third problem relates to the implementation of standard optical imagestabilization (OIS) in a dual-aperture zoom camera. Standard OIScompensates for camera tilt (“CT”) by a parallel-to-the image sensor(exemplarily in the X-Y plane) lens movement (“LMV”). Camera tilt causesimage blur. The amount of LMV (in mm) needed to counter a given cameratilt depends on the cameras lens EFL, according to the relationLMV=CT*EFL where “CT” is in radians and EFL is in mm. Since as shownabove a dual-aperture zoom camera may include two lenses withsignificantly different EFLs, it is impossible to move both lensestogether and achieve optimal tilt compensation for both Tele and Widecameras. That is, since the tilt is the same for both cameras, amovement that will cancel the tilt for the Wide camera will beinsufficient to cancel the tilt for the Tele camera. Similarly, amovement that will cancel the tilt for the Tele camera willover-compensate the tilt cancellation for the Wide camera. Assigning aseparate OIS actuator to each camera can achieve simultaneous tiltcompensation, but at the expense of a complicated and expensive camerasystem.

SUMMARY

Embodiments disclosed herein refer to thin dual-aperture zoom cameraswith improved drop impact resistance, smaller total thickness, smallerTTL difference between Wide and Tele cameras and improved OIScompensation.

In some embodiments there are provided dual-aperture zoom camerascomprising a Wide camera with a respective Wide lens and a Tele camerawith a respective Tele lens, the Wide and Tele cameras mounted directlyon a single printed circuit board, wherein the Wide and Tele lenses haverespective effective focal lengths EFL_(w) and EFL_(T) and respectivetotal track lengths TTL_(W) and TTL_(T) and wherein TTL_(W)/EFL_(W)>1.1and TTL_(T)/EFL_(T)<1.0.

In some embodiments, a dual-aperture zoom camera disclosed hereinfurther comprises an OIS controller configured to provide a compensationlens movement according to a camera tilt input and a user-defined zoomfactor through LMV=CT*EFL_(ZF), wherein EFL_(ZF) is a “zoom-factordependent EFL”.

In some embodiments, the Tele lens is a lens as described in detail inU.S. provisional patent application No. 61/842,987 and in U.S. patentapplication Ser. No. 14/367,924, titled “Miniature telephoto lensassembly”, both of which are incorporated herein by reference in theirentirety.

In some embodiments there are provided methods for manufacturing a dual-aperture zoom camera comprising the steps of providing a Wide camerahaving a Wide lens with an effective focal length EFL_(w) and a totaltrack length TTL_(W), providing a Tele camera having a Tele lens with aneffective focal length EFL_(T) and a total track length TTL_(T), whereinTTL_(W)/EFL_(W)>1.1 and wherein TTL_(T)/EFL_(T)<1.0, and mounting theWide and Tele cameras directly on a single printed circuit board.

In some embodiments, the methods further comprise the step ofconfiguring an OIS controller of the dual-aperture zoom camera tocompensate lens movement of the Wide and Tele lenses according to acamera tilt input and a user-defined zoom factor.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments are herein described, by way of example only,with reference to the accompanying drawings, wherein:

FIG. 1 shows definitions of TTL and EFL;

FIG. 2 shows shadowing and light-blocking problems caused by heightdifferences between Wide and Tele cameras in a dual-aperture camera;

FIG. 3 shows an embodiment of a dual-aperture camera disclosed herein;

FIG. 4 shows schematically in a block diagram details of the cameraembodiment of FIG. 3.

DETAILED DESCRIPTION

The present inventors have determined that camera movement (due toexemplarily, but not limited to mishaps such as drop impact) can beavoided or minimized by mounting the two cameras directly on a singleprinted circuit board and by minimizing a distance “d” therebetween.FIG. 3 shows an embodiment of a dual- aperture camera 300 that includestwo cameras 302 and 304 mounted directly on a single printed circuitboard 305. Each camera includes a lens assembly (respectively 306 and308), an actuator (respectively 310 and 312) and an image sensor(respectively 314 and 316). The two actuators are rigidly mounted on arigid base 318 that is flexibly connected to the printed board throughflexible elements 320. Base 318 is movable by an OIS mechanism (notshown) controlled by an OIS controller 402 (FIG. 4). The OIS controlleris coupled to, and receives camera tilt information from, a tilt sensor(exemplarily a gyroscope) 404 (FIG. 4). More details of an exemplary OISprocedure as disclosed herein are given below with reference to FIG. 4.The two cameras are separated by a small distance “d”, typically 1 mm.This small distance between cameras also reduces the perspective effect,enabling smoother zoom transition between cameras.

In some embodiments and optionally, a magnetic shield plate as describedin co-owned U.S. patent application Ser. No. 14/365,718 titled “Magneticshielding between voice coil motors in a dual-aperture camera”, which isincorporated herein by reference in its entirety, may be inserted in thegap with width d between the Wide and Tele cameras.

In general, camera dimensions shown in FIG. 3 may be as follows: alength L of the camera (in the Y direction) may vary between 13-25 mm, awidth W of the camera (in the X direction) may vary between 6-12 mm, anda height H of the camera (in the Z direction, perpendicular to the X-Yplane) may vary between 4-12 mm More typically in a smartphone cameradisclosed herein, L=18 mm, W=8.5 mm and H=7 mm.

The present inventors have further determined that in some embodiments,the problem posed by the large difference in the TTL/EFL ratio of knowndual-aperture camera Tele and Wide lenses may be solved through use of astandard lens for the Wide camera (TTL_(W)/EFL_(W)>1.1, typically 1.3)and of a special Tele lens design for the Tele camera(TTL_(T)/EFL_(T)<1, typically 0.87). Exemplarily, the special Tele lensdesign may be as described in co-owned U.S. patent application Ser. No.14/367,924, titled “Miniature telephoto lens assembly”, which isincorporated herein by reference in its entirety. A Tele lens assemblydescribed in detail therein comprises five lenses that include, in orderfrom an object side to an image side: a first lens element with positiverefractive power having a convex object-side surface, a second lenselement with negative refractive power having a thickness d₂ on anoptical axis and separated from the first lens element by a first airgap, a third lens element with negative refractive power and separatedfrom the second lens element by a second air gap, a fourth lens elementhaving a positive refractive power and separated from the third lenselement by a third air gap, and a fifth lens element having a negativerefractive power, separated from the fourth lens element by a fourth airgap, the fifth lens element having a thickness d₅ on the optical axis.The lens assembly may exemplarily have a F number (F#)<3.2. In anembodiment, the focal length of the first lens element f1 is smallerthan TTL_(T)/2, the first, third and fifth lens elements have each an

Abbe number greater than 50, the second and fourth lens elements haveeach an Abbe number smaller than 30, the first air gap is smaller thand₂/2, the third air gap is greater than TTL_(T)/5 and the fourth air gapis smaller than 1.5 d₅. In some embodiments, the surfaces of the lenselements may be aspheric.

Using a Tele lens designed as above, TTL_(T) is reduced to 7×0.87=6.09mm, leading to a camera height of less than 7 mm (acceptable in asmartphone). The height difference (vs. the Wide camera) is also reducedto approximately 1.65 mm, causing less shadowing and light blockingproblems.

In some embodiments of a dual-aperture camera disclosed herein, theratio “e”=EFL_(T)/EFL_(W) is in the range 1.3-2.0. In some embodiments,the ratio TTL_(T)/TTL_(W)<0.8e. In some embodiments, TTL_(T)/TTL_(W) isin the range 1.0-1.25. In general, in camera embodiments disclosedherein, EFL_(W) may be in the range 2.5-6 mm and EFL_(T) may be in therange 5-12 mm.

With reference now to FIG. 4, in operation, tilt sensor 404 dynamicallymeasures the camera tilt (which is the same for both the Wide and Telecameras). OIS controller 402, which is coupled to the actuators of bothcameras through base 318, receives a CT input from the tilt sensor and auser-defined zoom factor, and controls the lens movement of the twocameras to compensate for the tilt. The LMV is exemplarily in the X-Yplane. The OIS controller is configured to provide a LMV equal toCT*EFL_(ZF), where “EFL_(ZF)” is chosen according to the user-definedZF. In an exemplary OIS procedure, when ZF=1, LMV is determined by theWide camera EFL_(W) (i.e. EFL_(ZF)=EFL_(W)and LMV=CT*EFL_(W)). Furtherexemplarily, when ZF>e (i.e. ZF>EFL_(T)/EFL_(W)), LMV is determined byEFL_(T) (i.e. EFL_(ZF)=EFL_(T) and LMV=CT*EFL_(T)). Further exemplarilyyet, for a ZF between 1 and e, the EFL_(ZF) may shift gradually fromEFL_(W) to EFL_(T) according to EFL_(ZF)=ZF*EFL_(W). As mentioned, theOIS procedure above is exemplary, and other OIS procedures may use otherrelationships between EFL_(ZF) and ZF to provide other type of LMV.

While this disclosure has been described in terms of certain embodimentsand generally associated methods, alterations and permutations of theembodiments and methods will be apparent to those skilled in the art.The disclosure is to be understood as not limited by the specificembodiments described herein, but only by the scope of the appendedclaims.

What is claimed is:
 1. A dual-aperture zoom camera, comprising: a) aWide camera that includes a Wide lens with an effective focal lengthEFL_(W) and a total track length TTL_(W); and b) a Tele camera thatincludes a Tele lens with an effective focal length EFL_(T), a totaltrack length TTL_(T) and a F number smaller than 3.2, wherein therespective Wide and Tele lens total track lengths and effective focallengths fulfill the conditions TTL_(W)/EFL_(W)>1.1 andTTL_(T)/EFL_(T)<1.0.
 2. The dual-aperture zoom camera of claim 1,wherein a height difference between the Tele and Wide cameras is 1.65 mmor smaller.
 3. The dual-aperture zoom camera of claim 1, wherein a ratioe=EFL_(T)/EFL_(W) between the effective focal lengths of the Tele andWide cameras is in the range 1.3-2.0.
 4. The dual-aperture zoom cameraof claim 3, wherein a ratio TTL_(T)/TTL_(W) between the total tracklengths of the Tele and Wide cameras is smaller than 0.8e.